1. Field of the Invention
The present invention relates to a thermoelectric printer that applies a voltage to part of a ink ribbon to heat the part and transfer ink from the ribbon to a printing sheet. Particularly, the present invention relates to a thermoelectric printer, with an ink ribbon cartridge that is easily installed in and removed from the printer.
2. Description of the Prior Art
A thermoelectric ink ribbon employed for a thermoelectric printer generally comprises a resistive layer formed of a base film having proper electric resistance, a conductive layer made of an electrical conductor, such as aluminum, deposited on one side of the resistive layer, and an ink layer made of solid or semi-solid ink applied on the conductive layer. A printing head of the printer has many thin pins serving as recording electrodes. The pins are selected according to printing patterns and pressed against part of the resistive layer of the ink ribbon so that a recording voltage is applied to the resistive layer. Then, a recording current flows to the conductive layer through the resistive layer of the ink ribbon to generate Joule's heat in the resistive layer. The heat melts the ink layer of the ink ribbon to print the printing patterns on a printing sheet.
The recording current applied to the conductive layer is grounded through a return electrode contacting the ink ribbon.
The ink ribbon is generally received in a resin cartridge to be installed in a cartridge type thermoelectric printer.
According to the cartridge type thermoelectric printer, the cartridge supports a pair of reels around which the ink ribbon is wound and taken up from one to the other. The cartridge is removably installed in a carriage of the printer.
The carriage is guided by a carriage shaft and a rail arranged in parallel with each other. A motor drives a transmission belt that provides the carriage with a recording motion in a recording direction and a returning motion in the opposite direction. Behind the carriage, a platen runs parallel with the carriage shaft. In front of the platen, a printing sheet is set.
The carriage is provided with printing head means. The printing head means comprises an arm supported by a pin such that the arm can move toward the printing sheet, and a printing head fitted to the free end of the arm. While the carriage is in the recording motion, the arm is driven by an actuator to move the printing head toward the printing sheet. Then, the ink ribbon located between the printing head, and the printing sheet is moved to an ink transferring position adjacent to the printing sheet.
The carriage is provided with a return electrode made of a roller, for discharging a recording current flowing through the ink ribbon. The return electrode is arranged in the vicinity of the resistive layer of the ink ribbon when the cartridge is installed to the carriage. The return electrode faces a pinch roller with the ink ribbon between them. The pinch roller is pushed against the return electrode. By manually operating a control lever, the pinch roller is removed from the return electrode and held at the removed position through an interlocking mechanism provided for the carriage.
The conventional cartridge type thermoelectric printer mentioned in the above has a drawback that it requires installing and removing the cartridge in and from the carriage is troublesome.
Namely, to install the cartridge in the carriage, the control lever of the pinch roller is operated to separate the pinch roller from the return electrode. Then, the cartridge is installed in the carriage, and the ink ribbon is inserted between the pinch roller and the return electrode. The control lever is released to press the pinch roller against the return electrode such that the return electrode and the ink ribbon contact with each other.
To remove the cartridge from the carriage, the control lever is operated to separate the pinch roller from the return electrode. Then, the cartridge is removed from the carriage.